Nonpolar olefin polymers, e.g., polypropylene resin, and polar acrylate ester copolymers, e.g., ethylene/alkyl acrylate elastomers, when blended do not form mixtures that have adequate physical properties required for many commercial uses. The low degree of compatibility of the polymers with each other is evident from the lack of development in the blends of good physical properties, especially tensile strength and elongation at break and, consequently, such blends cannot be used for many applications such as tubing, seals, hose covers, and wire and cable coverings when high tensile strength and elongation at break are required. In order to obtain optimum physical properties when an alkyl acrylate elastomer and a polyolefin resin are blended, as disclosed in U.S. Pat. No. 4,555,546, it has been necessary to add a compatibilizing agent to the polymer mixture.
The compatibilizing agents for polyolefins, e.g., polypropylene, and ethylene/alkyl acrylate elastomers, e.g., ethylene/methyl acrylate/cure site monomer, are copolymers that have at least one olefin polymer compatibilizing segment derived from a homopolymer or copolymer of a C.sub.2 -C.sub.8 alpha-monoolefin or polybutadiene, polyisoprene or a polyalkenamer, and at least one acrylic ester copolymer rubber compatibilizing segment derived from a polymer selected from epichlorohydrin polymers, nitrile rubber, urethane polymers, vinyl chloride polymers, polyamides, polyamines, polyesters, and crosslinkable acrylic ester copolymer rubbers. The requirement that the blend of polymers must contain a compatibilizing agent to make a product having excellent physical properties adds to the expense of the polymer blend and requires an extra step for manufacturing the thermoplastic composition.
It has now been discovered that blends of certain nonpolar crystalline polyolefin resins, e.g., polypropylene, and dynamically crosslinked elastomer polar polymers which comprise ethylene, an alkyl acrylate, and a cure site can be prepared that have excellent tensile strength values and elongation at break values without the necessity of incorporating into the thermoplastic composition a compatibilizing agent. These thermoplastic compositions are especially useful for molding parts such as seals, gaskets, and sheeting for automotive applications, e.g., doors or fenders, and wire and cable covering.